1. Field of the Invention
This invention relates to an improved method of sterilizing articles employed in surgery, treatment, and diagnosis.
2. Description of the Prior Art
It is well known that the dipping of articles into concentrated solutions of hydrogen peroxide (10% to 40%) will sterilize such articles; see, for example, U.S. Pat. Nos. 3,854,874 and 3,904,361. It is also known that hydrogen peroxide vapors will effect such sterilization; see, U.S. Pat. Nos. 4,169,123 and 4,169,124. Reference is particularly made to the latter two patents which compare the bactericidal or sporicidal action of both liquid and gaseous hydrogen peroxide and further note that the sporicidal activity, as recommended by the Food and Drug Administration, of a sterilizing process must assure a probability of less than one organism out of one million surviving the sterilization cycle.
While the dipping of articles to be sterilized in solutions of liquid hydrogen peroxide is effective to reduce bacterial spore concentration to about 10.sup.-6 or better, there are disadvantages to be encountered in this process: (1) dipping objects to be sterilized in a bulk liquid can lead to the contamination of the entire solution and prevent its future use, (2) dipping objects exposes workers and the surrounding environment to the usual hazards of working with fairly large quantities of the sterilant hydrogen peroxide and its attending vapors, and (3) dipped objects may have to be rinsed with sterile distilled water before drying to ensure that any nonvolatile materials present in the sterilization solution will not remain on the object following the required drying step. Inasmuch as hydrogen peroxide is unstable in solution it is necessary to employ stabilizers to control its rate of decomposition. While such deposition of solid stabilizers on the products to be sterilized is avoided in the forementioned U.S. Pat. Nos. 4,169,123 and 4,169,124, the advantage of bringing the articles to be sterilized into positive contact with liquid hydrogen peroxide solutions is not thereby obtained. When, in addition, hydrogen peroxide aerosols are employed (NASA Technical Translation TTF-15, 127, of Fedyayev et al., Virucidal Action of Hydrogen Peroxide Aerosols in Decontamination of Air in an Influenza Nidus, Zhurnal Mikrobiologii, Eipidemologii i Immunobiologii, 9, 137-142 (1972) there is no assurance that the aerosols will not carry with them dispersed particles containing stabilizer components.
In addition, dipping methods introduce the inherent unreliability of individual action in that, for example, articles may not be completely dipped in solution or they may be protected by small air pockets and solution thereby does not contact every surface or penetrate every crevice of the article; or the article may not be immersed for a sufficient period of time in the solution.
The notable sporicidal action of gaseous hydrogen peroxide, as taught in U.S. Pat. Nos. 4,169,123 and 4,169,124 may be explained by the fact that the sterilization chamber preferably is evacuated before introduction of the sterilant. This means that the gaseous sterilant is not impeded by diffusion through air in reaching the articles to be sterilized. Further, intimate contact is possible between the gaseous sterilant and the surface of an article to be sterilized without the interference of air entrapped in interstices adjacent such surface.
Since the sporcidal activity of hydrogen peroxide is chemical in nature, the rate of such (killing) activity is increased by an increase in the concentration of the sterilant at the point of attack. The present invention is directed to accomplishing such an increase in sterilant concentration by creating a liquid hydrogen peroxide condensate in the presence of a vacuum, the liquid being more highly concentrated than the hydrogen peroxide vapor taught in U.S. Pat. Nos. 4,169,123 and 4,169,124. In other words, the present invention may be considered a "dip process" with each "dip" applying a fresh, pure liquid sterilant to an evacuated (air free) surface.